1. Field of the Invention
This disclosure relates to a method and apparatus for connecting an internally threaded fastener element to a wall by cold expanding a non-threaded tubular portion of the fastener element within an opening in the wall and providing the fastener element with wall contacting flanges on both sides of the wall.
2. Description of the Related Art
The aerospace industry utilizes a fastener that is in the nature of a tubular rivet with internal threads. The fastener can be installed in seconds into an opening in a wall from one side of the wall. No finishing work is required once the fastener is installed. It is ready for use With clean threads available for screw attachment. This tubular rivet has a flange on one end. The opposite end is inserted into the opening in the access side of the wall and the tubular rivet is pushed into the opening until the flange is against the access of the wall. A rod with a threaded end is then inserted into the tubular rivet from the access side of the wall and is connected to threads inside the tubular rivet. Then, a hand or power tool is operated to pull on the rod. This causes a reduced wall portion of the tubular rivet on the blind side of the wall to radially bulge and form a second flange that tightly engages the blind side of the wall. A tubular rivet system of this type is currently provided by RIVNUT.RTM. Engineered Products, Inc. of Kendallville, Ind. An early form of this type of system is disclosed by U.S. Pat. No. 2,384,347, granted Sep. 4, 1945, to Michael Schultz. A problem with known tubular rivets is that they often rotate in the opening when torque is applied to a screw that is connected to the tubular rivet after it has been installed.
It is known to install a nut holder on a wall at the location of an opening in the wall and then connect a nut to the installed nut holder. A tubular stem portion of the nut holder is inserted into the opening in the wall and is then radially expanded to connect it to the wall and also cold work the wall material surrounding the opening for fatigue life enhancement. Then the nut is connected to the nut holder to provide bolt receiving threads. Examples of this type of system are disclosed by U.S. Pat. No. 5,096,349, granted Mar. 17, 1992, to Michael A. Landy, Roger T. Bolstad, Charles M. Copple, Darryle Quincey, Eric T. Esterbrook, Leonard F. Reid and Louis A. Champoux, and by U.S. Pat. No. 5,468,104, granted Nov. 21, 1995, to Leonard F. Reid and Charles M. Copple. The radial expansion locks the nut holder against rotating but these systems require attachment of a nut to provide the wall insert with the internal threads.
There is a need for a method and apparatus for installing a fastener element with internal threads in an opening in a wall in such a way that the tubular rivet is restrained against rotating in response to a bolt being threaded into the fastener element. An object of the present invention is to provide such a method and apparatus.